Skip to main content

Stefan-Boltzmann Law Part I

This came up in the climate-change discussion group I've mentioned before.

One participant in a heated exchange, seeking to boost his own scientific cred, challenged the other to explain the Stefan-Boltzmann Law. The second fellow refused to participate in that discussion, saying, "I suspect you copied the question from elsewhere, and would be unable to actually converse on the topic ... are you real or are you Memorex?"

That last reference tells me something about his age, at least.

Anyway, now I'm curious, so I do a little research. The S-B Law describes the radiation from a black body as directly proportional to the fourth power of that black body's thermodynamic temperature. Huh?

A "black body" is an ideal state, somewhat akin to those "frictionless surfaces" you encounter in "Intro to Physics" courses. But you don't get to this ideal state until you get to "Intro to Thermodynamics."

A black body is one that absorbs all incident radiation. A white body, on the other hand, reflects all incident rays. Most actual bodies are thermodynamically gray. For many gray bodies the S-B law works as a good approximation.

So, the law basically says that radiation does the job if reflection fails. That is: if a body doesn't reflect energy away, then it becomes hotter over time, and as it becomes hotter, it radiates energy outward, creating the constant mathematical relationship with which we began.

Curiosity sated? Well ... just a bit.

But what does all this have to do with global warming? Or was it just an arbitrary quiz that one internet blowhard was trying to administer to another?


Popular posts from this blog

A Story About Coleridge

This is a quote from a memoir by Dorothy Wordsworth, reflecting on a trip she took with two famous poets, her brother, William Wordsworth, and their similarly gifted companion, Samuel Taylor Coleridge.

We sat upon a bench, placed for the sake of one of these views, whence we looked down upon the waterfall, and over the open country ... A lady and gentleman, more expeditious tourists than ourselves, came to the spot; they left us at the seat, and we found them again at another station above the Falls. Coleridge, who is always good-natured enough to enter into conversation with anybody whom he meets in his way, began to talk with the gentleman, who observed that it was a majestic waterfall. Coleridge was delighted with the accuracy of the epithet, particularly as he had been settling in his own mind the precise meaning of the words grand, majestic, sublime, etc., and had discussed the subject with William at some length the day before. “Yes, sir,” says Coleridge, “it is a majestic wate…

Cancer Breakthrough

Hopeful news in recent days about an old and dear desideratum: a cure for cancer. Or at least for a cancer, and a nasty one at that.

The news comes about because investors in GlaxoSmithKline are greedy for profits, and has already inspired a bit of deregulation to boot. 

The FDA has paved the road for a speedy review of a new BCMA drug for multiple myeloma, essentially cancer of the bone marrow. This means that the US govt has removed some of the hurdles that would otherwise (by decision of the same govt) face a company trying to proceed with these trials expeditiously. 

This has been done because the Phase I clinical trial results have been very promising. The report I've seen indicates that details of these results will be shared with the world on Dec. 11 at the annual meeting of the American Society of Hematology. 

The European Medicines Agency has also given priority treatment to the drug in question. 

GSK's website identifies the drug at issue as "GSK2857916," althou…

Hume's Cutlery

David Hume is renowned for two pieces of cutlery, the guillotine and the fork.

Hume's guillotine is the sharp cut he makes between "is" statements and "ought" statements, to make the point that the former never ground the latter.

His "fork" is the division between what later came to be called "analytic" and "synthetic" statements, with the ominous observation that any books containing statements that cannot be assigned to one or the other prong should be burnt.

Actually, I should acknowledge that there is some dispute as to how well or poorly the dichotomy Hume outlines really maps onto the analytic/synthetic dichotomy. Some writers maintain that Hume meant something quite different and has been hijacked. Personally, I've never seen the alleged difference however hard they've worked to point it out to me.

The guillotine makes for a more dramatic graphic than a mere fork, hence the bit of clip art above.

I'm curious whe…